PostSharp4Unity modifies assemblies after compilation to make objects
self-configurable: you don't need to call a factory method; you can use the
default constructor. All you have to do is to decorate your class with the
custom attribute "Configurable". It smells like Spring, isn't it ;-).
It is available from
http://code.google.com/p/postsharp-user-plugins/.
I have updated the StopLight sample. The first change is on the
StoplightForm class:

As you can see, there is a little of set up to do, but it's only once per
assembly. (And would be useless if there were some Unity-wide notion of
context registry or default container.) At this price, you can use Unity
with any object without having to construct them using a factory method.
Pay attention that your
'configurable' objects are now configured before the constructor is
executed, and not after. So, in the class StoplightForm, we have to
move the view initialization at the end of the constructor: